Not Applicable
Not Applicable
Not Applicable
The present invention is in the field of fuel level responsive valves used in vehicle fuel tanks.
Fuel level responsive valves are well known in the art of controlling the venting of fuel vapor from vehicle fuel tanks. These valves typically have a float mechanism trapped within a valve body to move a valve closure element into and out of sealing engagement with a vent outlet in response to rising and falling fuel levels. Such valves are most often employed as rollover valves, responding to fuel slosh or vehicle tilt and rollover situations to protect a vapor-processing canister from liquid fuel, although they can also be used for fill control shutoff and primary onboard vapor control.
Some successful float-operated valves are shown in U.S. Pat. No. 4,753,262 issued to Bergsma, and U.S. Pat. No. 5,313,977 issued to Bergsma, et al., both co-owned with the present application. These valves employ a peelaway type opening action, in which a rigid plastic plate- or paddle-like valve element is initially xe2x80x9ccrackedxe2x80x9d open over a limited segment of its sealing surface with the vent outlet by an actuator attached to the float, and subsequently xe2x80x9cpeeledxe2x80x9d from the vent outlet, either circumferentially or in lever fashion. By initially cracking or peeling only a portion of the valve element from the vent outlet, the pressure differential acting across the valve element is reduced to prevent the float from becoming xe2x80x9chung upxe2x80x9d, or lodged in the closed position, unable to overcome the force of the pressure differential acting across the surface area of the valve element to open the valve when fuel level drops. The net downward force comprising the weight of the float, less buoyancy forces is not sufficient to move the entire valve element off the vent outlet at once, because the accumulated force of the vapor pressure differential acting across the entire surface area of the valve element is substantially greater.
Heretofore rigid valve elements have been employed because they are more responsive to the initial xe2x80x9ccrackingxe2x80x9d or xe2x80x9cpeelingxe2x80x9d action of the float. It is therefore necessary to either machine the sealing surfaces of the rigid valve element and the vent outlet carefully to ensure an adequate vapor and liquid seal, or to apply an additional resilient, rubberlike seal member to either the valve element or the vent outlet to improve the seal between them.
Another prior approach has been the use of pliable, ribbonlike valve elements which are opened in a generally continuous peeling fashion. Examples of such valves are shown in the above-described patent to Bergsma, et al. and in U.S. Pat. No. 4,770,201 and published European Patent Application EP 0724098A1 to Zakai, et al.
While pliable, rubber-type valve elements provide improved sealing with the vent outlet, rubber-type seals have tended to provide a continuous peeling action which has been found not as desirable as the cracked-open lever action of rigid valve elements. Such seals have also been found prone to xe2x80x9cbunching upxe2x80x9d or deforming due to high volume vapor flow, large pressure differentials, and any horizontal sliding motion of the float relative to the vent outlet.
The present invention solves the foregoing disadvantages of the prior art valve with a valve element having a pliable, resilient diaphragm-like seal member peripherally stiffened by a thickened rim to give the resilient seal a lever-type opening action.
In a preferred form, the float has a generally ring-shaped cage or frame which traps the resilient seal member. The trapped resilient seal is preferably stiffened, for example with a thickened edge to provide body or shape holding characteristics to a thin, pliable center section which engages the vent outlet.
The seal member is trapped inside the cage for limited vertical, and preferable also limited horizontal movement within the cage to assist with the opening action.
In the preferred form the cage is integrally formed with the float and has a flexible strip portion or xe2x80x9cliving hingexe2x80x9d portion which is folded and snap-locked in place after insertion of the seal member in the cage for retaining the seal member in the cage.